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A Geologic Safari of the East African Rift and the Newark Basin
Answer these questions before viewing the PowerPoint presentation:
1. Think about what you know about divergent plate boundaries. Explain, in your own
words, what is happening to the lithosphere (crust and upper-most mantle) at a
continental divergent boundary (rift).
2. As the lithosphere extends or rifts, what kind of faults would you expect to find
accommodating this extension?
3. What kind of volcanoes would you expect to see at a rift? What kind of magma or
lava do you think you would find?
4. Do you think you would see any other kind of volcanic features?
5. What kind of igneous rocks would you expect to find at a continental rift?
6. Can you think of any other landscape features that you might see?
Answer these questions as you view the PowerPoint presentation:
7. Look at the maps of the faults that define the East African Rift Valley. They run north
and south for hundreds of miles. A cross section of the rift valley is shown in slide #6 what kind of faults do you see?
8. The picture on slide #7 shows a picture of a fault, and the person in the photo is
standing on the hanging wall. What kind of fault do you think this is? Is it the same kind
of faults that you identified in question #7 above?
9. There are many volcanoes inside the East African Rift. Look at the pictures of the
volcanoes in slides 11-13. What kind of volcanoes do you think these are? How do you
know?
10. Look at the lava from the Erte Ale volcano in slide #14. What do you think the
composition of this lava is? Is it felsic, intermediate, or mafic? Does this make sense
with your answer for question #9?
11. Other types of volcanic features that are common in Eastern Africa are fissure
eruptions that extrude large amounts of lava, and intrusive dikes and sills. What kind of
rock do you think makes up the sill on slide #11?
12. Millions of years from now, futures geologists will investigate Eastern Africa. They
will suspect that the area used to be part of a continental rift. What geologic evidence
should they look for to support their claim? What geologic structures will still be left to
investigate? What geologic structures are currently being created that these geologists
can study?
13. Much of the Appalachian Piedmont Province in the Eastern United States is the
remnant of a rift valley that formed when Pangaea broke apart over 200 million years
ago. What is now central New Jersey used to be at the edge of the rift, and it probably
looked very similar to the way portions of the East African Rift look today.
Look at the geologic map on slide #22. Why would the shale and other mudrocks cover
most of this area that used to be part of a rift? Do you think shale could be forming right
now in Eastern Africa? Where?
14. Several major faults helped to accommodate the extension that occurred when
Pangaea broke apart. Look at slides 23-25. What kind of faults do you see? How do
these compare with the faults you saw earlier in Eastern Africa?
15. Many intrusive and extrusive igneous rocks can be found in the Newark rift basin.
The Watchung Mountains formed from fissure eruptions, and several intrusive igneous
dikes and sills have been unroofed. Since these mafic igneous rocks are more resistant to
erosion than the surrounding sedimentary rocks, they form many of the ridges and hills
that are visible in New Jersey today, though they were once below ground.
Overall, what similarities do you see between the geology of the East African rift and the
geology of the Newark Basin? Do you see any differences?